What Could Cause Breath Shortness?

I am a 37 year old female. I have no idea what this is and I am really scared! Its been happening for awhile now but only in the last few days has it increased. I have heart palpatations almost constantly. It beats faster normal. Its possible I'm feeling shortness of breath and just today I've noticed a tingling and numbing sensation in my left arm (below elbow) and in my fingers. My hands are also shaky. More the left one than the right. I can't always keep my hands steady especially when I am writing or gripping something. I also have an achy back on the left side near the shoulder blade and some in and out pains below the left breast (top of the rib). Some of these pains have been on the right too but more on the left. I also experience nausea sometimes too. I am sooo scared of what this is and I am very young for this to happen to. I don't feel like this is something I should rush to the ER for. Especially since I haven't blacked out, fainted, or had worse symptoms but I am still very freaked out by this. Don't know what to do or if this is gonna go away or get better or what. If anyone has had the same thing or can ease my mind in any way, I'd appreciate any help, thx!